The present invention relates to glass batch forming methods. In particular, it relates to a method wherein a calcium magnesium silicate is substituted for lithium as a melting aid in glass batches.
Glass batches can contain certain materials as melting aids. These aids assist in creating a homogeneous batch having complete reactions and performed at lower melting temperatures or times. One such melting aid is lithium, which while effective is relatively expensive to use. There remains a need to further develop useful melting aids which can be used in conjunction with or in the absence of lithium compounds.
One object of the present invention is a method of producing a glass batch composition having favorable viscosity characteristics. Another objective is to provide a melting aid for a glass batch which can work in conjunction with or as a partial or total replacement for lithium melting aids. These and other objectives are achieved by a method of forming a glass batch composition by the admixing of a calcium magnesium silicate composition.
One embodiment of the present invention is a method of producing a glass batch composition composed of a calcium magnesium silicate and other glass components to produce a glass batch. The glass batch composition is then melted to form a melted glass batch composition. The amount of said calcium magnesium silicate used is selected effectively to produce a viscosity character and batch free time in the glass batch composition less than or equal to that which results from use of an equivalent amount of a lithium compound in a comparative glass batch. An equivalent amount is the use of the same mass percent of the calcium magnesium silicate or lithium compound in the total glass batch before heating.
The calcium magnesium silicate of the present invention can be a natural resource or one attained by synthetic production. A preferred calcium magnesium silicate compound is that described in U. S. Pat. No. 6,211,103 B1 (Fairchild, et al.). A more preferred calcium magnesium silicate has an empirical formula of CaxMgySiO2, and the values of x and y are independently from about 0.1 to about 0.6 and z is a value to balance the oxidation state of the compound.
The respective amounts of the calcium magnesium silicate compound and other glass components is dependent upon the glass formula being produced. As used herein, the term xe2x80x9ccomparative glass batchxe2x80x9d or xe2x80x9ccomparative glass productxe2x80x9d means a glass batch or product which is equivalent in oxide values, except that the value of boron oxide equivalent is less for an embodied glass product made with the present invention than that made with known processes which do not use a calcium magnesium silicate compound as described herein. It has been unexpectedly discovered that by using the calcium magnesium silicate compound described herein that less lithium values are needed to attain the same or better result as the amount used in known methods. Accordingly, a preferred method is one in which the other batch components comprise less than about one percent by total batch weight of lithium. It was further unexpectedly found that in the method using calcium oxide silicate compounds to reduce the amount of lithium needed for a particular purpose, that the use of an embodied calcium magnesium silicate compound enabled as a preferred method to reduce the amount of said magnesium oxide compound to about zero.
The amount of the calcium magnesium silicate compound used can be adjusted so that the viscosity of the formed glass batch is at least about ten percent less than that of the comparative glass batch. Similarly, the amount of the calcium magnesium silicate compound used can be adjusted so that the batch free time of the formed glass batch is at least about ten percent less than that of the comparative glass batch.
In a preferred method, an amount of feldspathic compound can be combined with the calcium magnesium silicate compound to achieve similar results. In another preferred embodiment, the above method is modified by the additional mixing of a feldspathic component. Such feldspathic material can be of one of any of the numerous material or synthetic forms of feldspar or feldspar-type material. Such feldspathic material is an aluminosilicate with barium, calcium, potassium, or sodium component preferably is a potassium aluminosilicate having the formula KAlSi3O8 with little sodium values.